A current reference circuit, implemented using bipolar transistors, is known from U.S. Pat. No. 4,335,346. U.S. Pat. No. 4,335,346 describes a circuit which has two sub-circuits. A first sub-circuit has a negative temperature coefficient, that is the current generated thereby varies inversely with temperature, and a second sub-circuit has a positive temperature coefficient, that is the current generated thereby varies directly with temperature. The first sub-circuit comprises an NPN transistor, the emitter terminal of which is connected through a resistor to ground. As is well known, the base-emitter voltage of a bipolar transistor varies inversely with the temperature. Thus, the current through the transistor, which depends on the voltage across the resistor and the resistance value thereof, will also vary inversely with the temperature. The circuit further includes means for summing the currents generated by the first and second sub-circuits to produce an output current.